1. Field of the Invention
The present invention relates to a graphics system, and in particular discloses a graphics system capable of producing a rasterized image in real time.
2. Description of the Related Art
Most object based graphics systems utilize a frame store to hold a pixel based image of the page or screen. The outlines of the objects am calculated, filled in and written into the frame store. For two-dimensional graphics, objects which appear in front of other objects are simply written into the frame store after the background object, thereby replacing the background on a pixel-by-pixel basis. This is commonly known in the art as "Painter's algorithm". Images are calculated in object order, from the rearmost object to the foremost object. However, real-time image generation for raster displays requires that the images be calculated in raster order. This means that each scan-line must be calculated as it is reached. This requires that the intersection points of each scan line with each object outline are calculated and subsequently filled.
Although it is possible, with a line buffer rather than a page buffer, to use the Painter's algorithm within a scan-line to fill the objects, such an approach does not achieve image generation in real-time, particularly at video data rates.